稀土铈对9Cr1Mo钢组织及电化学腐蚀性能的影响

制备了稀土铈质量分数分别为0,0.002 0%,0.016 0%的9Cr1Mo钢,采用扫描电镜、能谱分析仪以及电化学工作站等研究了稀土铈对9Cr1Mo钢显微组织及在3.5%(质量分数)NaCl溶液中电化学腐蚀性能的影响。结果表明:稀土铈可以细化试验钢晶粒,减小马氏体片层间距以及晶界和晶内析出相的数量,提高试验钢的电化学腐蚀性能;含稀土铈质量分数为0.002 0%的试验钢具有最佳的耐腐蚀性能。     

35CrMoCe稀土钢离子硫氮碳复合渗特性研究

采用金相显微镜，Ｘ射线衍射仪，透明电子显微镜，扫描电子显微镜等仪器分析对比３５ＣｒＭｏ钢和３５ＣｒＭｏＣｅ钢离子硫氮碳复合渗特性，探讨了稀土铈和加速离子硫氮碳复合渗的原因，研究结果表明，两种钢的复合渗层均由硫化物层，氮碳化物层的扩展层构成；稀土铈显著地提高了渗层深度，铈具有细化组织的作用，提供了更多可供氮碳原子扩散的通道。     

铈、镧及富铈混合稀土对AZ91D合金组织和力学性能的影响

用SEM、XRD和EDS分析了添加0.5%,1.0%,1.5%铈、镧和富铈稀土的AZ91D合金的微观组织形貌和相组成;并测试了各合金的硬度以及不同温度下的拉伸性能。结果表明:铈、镧和富铈稀土的添加均能细化AZ91D合金α相,降低β相含量,同时形成针杆状Al11RE3化合物。添加同一稀土元素的合金中,当稀土含量为1.0%时,其常温和高温抗拉强度达到最大值。对比相同含量不同元素的作用,低含量时含铈合金抗拉强度较好,高含量时含镧合金常温和高温断后伸长率较高;铈、富铈混合稀土、镧提高合金硬度的作用依次减弱。     

钢中稀土铈与砷相互作用研究

利用中频真空感应熔炼炉、金相显微镜、电子探针等实验设备,研究了稀土元素铈与砷在钢中的相互作用。结果表明,在钢中铈、砷含量较高的条件下,铸态试样中铈可与铁生成金属间化合物Ce2Fe17,随机分布于铁基中,铈、砷和铁三种元素能发生交互作用,铈对砷在铁中的分布有固定作用。     

稀土蠕化剂对蠕墨铸铁生产的影响

目前对稀土元素在蠕墨铸铁中的应用已经有了较深的研究,但是不少人忽略了这样一个问题：稀土不是一种元素,而是一系列元素的总称,稀土中不同元素对蠕墨铸铁生产的影响不同。本文通过生产实践中遇到的问题来说明稀土中镧和铈的量对蠕墨铸铁生产的质量影响。     

稀土元素铈对超级双相不锈钢热变形能力的影响

利用Gleeble-3800热模拟试验机、光学显微镜、扫描电镜和能谱仪等研究了稀土元素铈对铸态00Cr25Ni7Mo4N超级双相不锈钢在应变速率为5 s-1、变形温度为1 100,1 150,1 200℃下热变形行为的影响。结果表明:稀土元素铈能够降低该钢中氧、硫含量,使钢中的夹杂物由硫化物变成稀土夹杂物,从而在一定程度上改善了该钢的热变形能力;铈的较佳添加量为0.165%~0.220%,适宜的热变形温度为1 150~1 200℃。     

国外动态

氢脆是妨碍发挥高强度钢强度潜力的重要因素。美国TRw公司系统研究了稀土添加剂对4340钢氢脆的影响,证明含0.2％铈或镧时,断裂试验的门槛应力强度提高三倍,裂纹长大造度降低一个数量级。但是其它机械性能却随稀土含量的提     

X射线荧光光谱法快速半定量分析催化剂中的稀土总量

介绍了用X射线荧光光谱仪测量催化剂中稀土总量的快速半定量分析方法。该方法根据自然界中稀土元素丰度与稀土总量之间的关系，通过选择镧、铈两个元素作为指示元素进行测定，就可以基本确定稀土元素的总量。实验结果证明，该方法快速简便、工作效率高。测量结果与给出的参考值吻合较好。     

稀土铈对热浸镀铝层组织和性能的影响

研究了稀土铈对热浸镀铝层组织结构、耐蚀和耐热性能的影响。结果表明：稀土铈质量分数低于0．3％时,热浸镀铝层的耐蚀性能和高温抗氧化性能都得到提高,超过此含量镀层的性能下降。稀土铈使得过渡层由锯齿形结构转变为平滑结构,使镀层中FeAl3析出相在表层中呈网状分布,随其含量增加过渡层厚度减小。稀土含量超过0．3％时,稀土化合物在表层中呈条块状第二相析出并偏聚,并且随著稀土铈含量增加,表面层中稀土化合物呈块状,且偏聚程度加大。     

GCr15模具钢冷拔模稀土盐浴渗钒

本文研究了GCr15冷拔模钢的渗钒盐浴中添加适量稀土铈合金,能改变钢表面化学物理状态,使之活化起到催渗作用。据实验,能提高渗速20％左右。处理后的冷拔模,具有优异的抗咬合性和耐磨性,使用寿命提高2倍以上。     

氧化铈对高强钢复合焊接焊缝组织与韧性的影响*

稀土是理想的变质和微合金化元素,采用Nd:YAG激光-MAG电弧复合焊接方法,以预置方式向高强钢复合焊接熔池过渡氧化铈,研究焊缝组织与低温(-40 ℃)冲击性能。结果表明：适量氧化铈能控制晶粒尺寸并细化焊缝组织,当添加量为0.3%时,焊缝晶粒得到明显细化,随着添加量的增加,晶粒尺寸和枝晶间距均增大,但氧化铈并不能改变焊缝组织相成分,仍以板条马氏体组织为主。氧化铈能够净化焊缝组织,变质夹杂物并起到异质形核作用,夹杂物主要由硅、铝、铁的氧化物或碳化物及少量含铈类氧化物和氧硫化物组成。低温冲击测试发现,焊缝及其热影响区冲击吸收能量随氧化铈添加量的增加而呈先增后降的变化趋势,当添加量为0.3%时,焊缝冲击吸收能量达到最大,而添加量为0.5%时,热影响区冲击吸收能量达到最大值,其断口处韧窝均多而深,以韧性断裂为主。     

应用ICP-MS测定国际比对果汁样品中铅、镉和锡的含量

建立了微波消解、电感耦合等离子体质谱法（ICP-MS）同时测定国际比对果汁样品中铅、镉和锡的方法。应用微波消解进行样品前处理,采用在线内标校正基体干扰,采用干扰方程抑制质谱干扰,使用工作曲线计算出样品中铅、镉和锡元素的含量。测定结果表明,铅、镉和锡元素的检出限分别为0.021、0.016和0.052μg/L,相对标准偏差（RSD〈5%）,加标回收率介于90%～105%,用该方法测定FAPAS国际比对果汁样品,反馈的统计结果显示铅、镉和锡元素的Z值分别为-0.4、0.1和-0.2,结果均为满意。该方法快速、简单、精确,适于果汁中铅、镉和锡的测定。     

Improvement of the manufacturing process of abrasive stones for honing

In the present work, the mixing process of different components of abrasive stones of cubic boron nitride used for rough honing was studied. Stones are made by the sintering process of abrasive grains, a metallic bond, and a humectant that favors covering of each abrasive grain by the bond. Incorrect mixing of abrasive grains with the bond and humectant can result in stones with nonuniform abrasive grain distribution. As the abrasive stone wears out, grain distribution will vary and modify efficiency of the honing operation. Tin is the metal having the lowest melting point among metals in the bond. By means of a scanning electron microscope and energy-dispersive X-ray microanalysis, tin segregation was discarded, which could have led to abrasive grain segregation. Later, mixing tests of the different components of the stones were performed at different mixing times. Both homogeneity degree of the abrasive content of different samples in a mix and covering degree of abrasive grains by bond were determined through two new parameters introduced in the present study. It was noted that use of a chain to accelerate the mixing process excessively reduces covering degree of abrasive grains even at initial mixing times. The highest quantity of humectant is recommended in order to get better covering degree. Mixing time should be high enough to assure homogeneity degree of the mix but low enough to avoid excessive reduction of covering degree.     

Nuclear susceptibility thermometry using enriched (119)Sn

Tin enriched to 84.5% (119)Sn has been used for static nuclear susceptibility thermometry. A calibration in the 2-40 mK range shows that it is linear in T(-1) quite accurately from 2 to 15 mK. The thermometer is easy to use and responds rapidly.     

Measurement of tight in steel ropes by a mean of thermovision

If tenseness in a wire causes its warming, the weakest place of the rope will react – it will became the warmest. If it is possible to predict the place/point of destruction of a rope or a chain by a means of tenseness causing warming, than it is also possible to search for disruptions on static ropes, but at suitable conditions. Destructive and non-destructive measurements were combined in order to detect disruptions on ropes and chains. Our experiments proved that at certain conditions the use of thermovision for detection of weak places on loaded ropes and chains is applicable. Above mentioned methodology was applied on static ropes in the place where it is not possible to perform regular NDT and at the places where ropes enter socket baskets.     

Continuous precipitation of ceria nanoparticles from a continuous flow micromixer

Cerium oxide nanoparticles were continuously precipitated from a solution of cerium(III) nitrate and ammonium hydroxide using a static microchannel T-mixer. T-mixer synthesis results were compared with synthesis results from batch precipitation. Findings show that the method of mixing is important in the ceria precipitation process. Uniform porous film structures and nanorods were produced when the particle chemistry was synthesized using T-mixing followed by spin coating. Batch mixing, when using higher NH₄OH feed concentrations followed by spin coating, was characterized by the heavy agglomeration of nanoparticles. Similar, high aspect ratio nanorods were produced when feed conditions in both batch mixing and T-mixing were identical demonstrating that the momentum effects of continuous microchannel T-mixing did not impact the synthesis process. In addition, it was found that the micromixing approach reduced the exposure of the Ce(OH)₃ precipitates to oxygen, yielding hydroxide precipitates in place of CeO₂ precipitates. The key advantage of the micro-scale T-mixing approach is higher throughput which is important for the scaling of ceria nanoparticle production.     

滇东南个旧市莫家锡多金属矿矿床地质特征及找矿标志

滇东南地区是云南省重要的有色金属矿产资源基地,具有良好的成矿条件,该区处于个旧锡多金属矿成矿带西部和著名的个旧锡矿西区的西缘,具有良好的成矿环境。矿区内锡多金属矿化与印支燕山火山岩浆活动关系密切,受断裂控制明显。地层岩性、构造特征、化探异常及物探异常是该矿区的重要找矿标志。     

Multifunctional materials: engineering applications and processing challenges

Multifunctional materials are designed so as to meet specific requirements through tailored properties. Smart materials can be considered as multifunctional ones that have the ability to react upon an external stimulus, simulating, in this way, the behavior of nature’s materials. Furthermore, the introduction of biomemetics in the material science, allows the designing of materials with similar processes as nature does: building from molecules to complete structures. This paper focuses on the presentation of the various multifunctional materials reported in the literature and the processing means developed.     

An experimental study on the AC electroosmotic flow around a pair of electrodes in a microchannel

This paper presents an experimental study on the AC electroosmotic flow in a microchannel having a pair of rectangular electrodes on the bottom wall with narrow gap. The microchannel was made of PDMS (Polydimethylsiloxane) and the electrodes of ITO (Indium Tin Oxide). The electrodes were arranged such that the electric field is mainly perpendicular to the channel’s longitudinal direction, thus creating a transversal secondary flow. The primary flow was driven by a pressure force through the fluid-level difference on both reservoirs of the channel. To measure the velocity distributions around the electrodes, we used a micro-PTV (particle tracking velocimetry) technique. We find that on the surface of the electrodes the flow velocity caused by the AC electroosmosis is directed from the electrode edge toward the side wall of the channel, and the maximum crosswise velocity occurs at the frequency 120Hz. A smooth profile of the crosswise velocity component along a vertical line was successfully obtained from the present experimental technique, and it shows a flow reversal due to the mass conservation principle.     

The precision cutting process as a non-linear closed loop system

The precision cutting process is a highly non-linear closed loop system. With a specially designed experimental set-up it was possible to impose variations on the depth of cut by means of an independent exciting signal. The dynamics perpendicular to the workpiece surface were identified with non-linearity tests and several model structures. It was found that these dynamics can be approximately modelled by a direction dependent damping and a non-linear stiffness. Furthermore, some consideration was given to the dynamics in cutting direction by means of several linear regressions. From the results it was possible to conclude that it is important (eg for control design) to model the cutting process as a non-linear closed loop system.